EDIT: saw your most recent post. my advice, if you really want to nail this thing down, is to either downgrade to a point in time where this wasnt happening OR keep what you have now and record what apps you're using and when. then compare to your bill and try to match up a time to an activity.

However, i always keep my previous 2 OS installs ready for restore should i need them.

It doesn't happen often, but there were a few versions of the 5.0 OS for the 9700 and 8900 that were absolute GARBAGE. even with hybrids, they were still crap. i would upgrade, run them for about 2 days and then downgrade back to the rock solid .624 build.

I say upgrade, but keep your backups nearby, else you will have to reinstall *everything* again.

Also, there are a ton of tutorials out there that show how to strip things out of a BB install. Basically all you need to do is delete / move the files you dont want installed.

I do this before i load up any OS, and i always have a smaller OS footprint because i strip out all the crap / un needed languages / games / apps / things RIM / the carriers put in.